[30713]

So, we all know that the Bolt is limited to 12A at 120V under the (probably correct) assumption that people are idiots and will blow a breaker.

As we know, many outlets (esp. TT-30) can crank out substantially more than 12A (up to 30A) - but the Bolt can't do anything with extra current - at 120V. However, at 240V, the Bolt can accept up to 32A.

Now, a NEMA 14-50 is not really 240V in a true sense, like it is in Europe. It is 2 x (hot) 120V.

Could An adapter easily be made that wires both hots in a 14-50 (female) in parallel from a 120V hot from a TT-30 (male)?

BIG CAVEAT: This cannot safely pull more than 30 Amps (it's all a TT-30 can supply). Connected to a NEMA 14-50, that means 15A per hot, which is realistically 12A per hot.

Now could a 12A level 2 portable EVSE can be plugged into an RV Park TT-30 (via adapter) if there are no 14-50 outlets available? This would mean 240 x 12A, or 2.88 kW, double the 120V limit (1.44 kW).

If you have an adjustable EVSE, as long as you keep it at 12A or less, the number of electrons drawn from the TT-30's hot (and delivered to the neutral) would not exceed the capacity, and you're off to the races?

 

[SparkE]

An adapter can easily be made that wires both hots in a 14-50 (female) in parallel from a 120V hot from a TT-30 (male).

BIG CAVEAT: This cannot safely pull more than 30 Amps (it's all a TT-30 can supply). Connected to a NEMA 14-50, that means 15A per hot, which is realistically 12A per hot.

You allude to this, but you should not pull more than 80% of 30 amps (0.8 * 30 = 24) for a continuous load. 24 amps, split the way you describe ('fake' 2 hots) would be 12 amps. To be blindingly obvious.

 

[30713]

Right - should have been more clear. Instantaneous draw of 15A can be managed, but continuous should not exceed 12A.

 

[ga2500ev]

So, we all know that the Bolt is limited to 12A at 120V under the (probably correct) assumption that people are idiots and will blow a breaker.

True.

As we know, many outlets (esp. TT-30) can crank out substantially more than 12A (up to 30A) - but the Bolt can't do anything with extra current - at 120V. However, at 240V, the Bolt can accept up to 32A.

Again true.

Now, a NEMA 14-50 is not really 240V in a true sense, like it is in Europe. It is 2 x (hot) 120V.

Not exactly. The two hots create a split phase 240V line. It is truly 240V. With a neutral at 0V, either of the hots plus the neutral provides 120V

An adapter can easily be made that wires both hots in a 14-50 (female) in parallel from a 120V hot from a TT-30 (male).

Interesting but problematic. What you get with this arrangement is a 120V line with the same phase on both hot lines. The question is whether or not the onboard charger would detect this as 240V. The problem is that the only return circuit for this setup is the ground line as neither the EVSE nor the onboard charger will have access to the neutral, which was replaced by the second hot. The moment the EVSE detects current on the ground line, which you are proposing to deliver upwards of 24 amps, the GFCI circuit in the EVSE is going to trigger, shutting down the EVSE.

The other possibility is that since there is not voltage difference between the two hot lines, the onboard charger will register this as 0V, with no charging at all.

In either case, not the result you hope for.

ga2500ev

 

[DucRider]

Splitting a 120V hot into two wires will not produce 240V, any more than splitting it into three will produce 360, four becoming 480, etc.

Those without even a basic understanding of electricity should NOT be making adapters - bad things can (and do) happen.

And for folks tempted to try the above - not everything you read on the internet is true (or safe). Most likely result in this scenario is the EVSE will see 120V, advertise whatever rate it is capable of (or set to), and the Bolt will draw 12A (or 8 if the default is not overridden). Other scenarios range from nothing happening at all, the magic smoke escaping from the EVSE, or worse. Depends somewhat on if the EVSE designers thought about someone feeding 120V in phase to both legs of the 240V circuitry.

 

[Vertiformed]

There seems to be a huge misunderstanding here about what a TT-30 plug is.

It provides 120 volts. If you wired a TT-30 to a NEMA 6-50 or NEMA 14-50 the car would see zero volts, as both hot pins would have no voltage difference between them. Note that the EVSE & car ignores the neutral pin of a NEMA 14-50 plug (because all it cares about is ground and the voltage between the two hots, and because EVSEs also work with NEMA 6-50 plugs that don't even have neutral).

So, if you made this adapter, you'd achieve nothing. As another poster said, if you thought this would work, you have no business making any kind of adapter.

FWIW, if you did want to use a TT-30, you'd need a step-up transformer to turn 120 volts into 240 (like this).

 

[30713]

Hadn't considered phase. Never mind.

 

[buk855]

There is a way to get more than 12A from a TT-30 but it requires a heavy transformer and an adjustable EVSE to set the current to 12A @ 240V or if you're willing to take the risk a little higher. You can take an isolation transformer or 120 to 240 step up transformer to obtain true 240V. The catch is we are talking a 40lb transformer here and you must pay extreme attention to every detail. The isolation transformer can be used to combine two independent 120V circuits into 240, even if they are the same phase, but again, this is not for those that don't have a strong understanding of what they are doing. Most people should not attempt any of this!

 

[RoadTripBiker]

43 years ago my wife and I lived in an apartment with a window unit air conditioner. Don't remember why but had to get a transformer to run the AC unit. I bought a transformer just to run the AC unit and it worked well for the few months we lived there.

Household power in the US is from a center tapped transformer. The center is tapped and each leg is 120V but the difference between the two legs is 240V. All single phase. The house my wife's parents lived in had three phase power! The AC unit was 3 phase.

 

[buk855]

43 years ago my wife and I lived in an apartment with a window unit air conditioner. Don't remember why but had to get a transformer to run the AC unit. I bought a transformer just to run the AC unit and it worked well for the few months we lived there.

Household power in the US is from a center tapped transformer. The center is tapped and each leg is 120V but the difference between the two legs is 240V. All single phase. The house my wife's parents lived in had three phase power! The AC unit was 3 phase.

EVSEs in the US can only handle single phase, but the source can be tapped from between two phases of three phase. When you find a L2 charger that outputs 208V you know the wiring it is connected to is three phase.

 

[EV Engineering]

You will need split phase between two 120V legs to make Bolt inverter see 210 V usually seen in US...two 120 legs from same side of step-down transformer will not result in 210. So don't do this it is more complex than what is worth it. That is why if you look at house power supplied there are 3 wires running from main transformer and newer codes require fourth wire with ground strip on the house.
Two hot wires are 120 V and have split phase and cannot be run over same wire.